Ain't meant to be contentious but I have a question...

[ptwining]

First off I think my UCD 180's are top-shelf - cleaner and prettier than almost anything else I've ever heard - out of the box.

Magnificent.

However, my NAD C270 power amp eats their lunch - clean (it's old power-amp but go look up the specs and reviews, 5-point raves).

Why is that? I am really and honestly curious.

Same speakers, same sources, same result. The NAD power amp (no integrated crap for me, thanks) takes the roof off (with sound that classd4sure would surely love) and the UCD's are much less, umm, well, deep and powerful.

The NAD generates crispier highs, lows more satisfying, at a much higher SPL.

I am NOT about loud (we've already discussed that). And don't get me wrong. I am on the class-d track without doubt. But, I'm gonna have to step up to a UCD400 to match my 120/w NAD. Twice the power to get the same quality result.

Why would that be?

Is there something magical about class A (A/B) sound. The NADs were designed by Thomlinson Holman after all.

My favorites are Holman for amps, and Burhoe for speaks.

Anyway, just curious...

Regards,
Tom

[KeithC]

I found the 400ADs to sound very similar to the 180ADs. The ColdAmp BP4078s however really brought the music to life.

I like the UcD modules - very precise, very low noise, but polite rather than involving. Good for background music when playing bridge.

The 4078s however seem to give deeper bass and really make live concerts more believable. More sensitive input level mind you, so it's difficult to do an a/b comparison with the UcDs.

To a great extent this is probably a matching issue with my main speakers - sensitive full range units with understated bass and forward upper mid range. I anticipate that the UcDs will match the second-string Quad C22s much better.

Class D amplifiers seem to be particularily sensitive to changes in psu. My 180s actually sounded better with a single TRN100A/HG supply than when I upgraded them to dual mono.

[ptwining]

In one sense I disagree - my UCD's rock-n-roll with the best of them - I love listening to them. Everything. Definitely not bridge music IMHO. They just don't do what I thought they might given their power rating.

Don't get confused here - I'm not on about Zeppelin blast - just big clean punch. Vollenweider style punch as opposed to Cheap Trick pound.

My UCD's are stock, no mods (I haven't the skills) but they are both running off one Avel toroid @ 30v secondaries.

Perhaps they want more electrons but I don't know what the ST power supply will tolerate (sure, I've read the specs but have no experience - makes me nervous to feed them more sauce with out asking first).

In any case - I wonder whether Bruno (or any of the big guys) has anything to say about the class A/B vs Class-d thing.

I suppose someone could easily say that I'm simply used to the NAD C270 - had it for years and years - but many independent ears (musicians and engineers) have agreed - but only on the power issue.

The sound quality of the UCD's has never been questioned, ever. Just the power.

In fact the most common comment has been - "Damn! That's fine."

If I was talking about comparing the UCD to an old Marantz or some crap I'd understand - but the C270 is a reference. I can listen to the NAD at full throttle and sleep - grooving away as the windows blow off the house. Finest kind Di Wee...

[me shrugs]

Maybe it's my DAC or my source equipment, not good enuff to feed the UCD what it wants. But there ain't no going back.

Just me curious to learn more and wanting to get the best out of this awesome gizzy...

How cool, it's so d**** good that all I want is more!

That's the kind of problem to have.



Regards,
Tom

[noah katz]

"How cool, it's so d**** good that all I want is more!"

So what's wrong with the obvious answers - more voltage to the UCD180's (they're rated for 50V after all), or the UCD400's?

[KeithC]

It's possibly a power issue rather than voltage.

Whats the VA rating of your transformer?

[ptwining]

It's an Avel 250VA with 2x30v secondaries. I got it from Kevin.

The only problem with the 400's is (smile) money.

I also already have 4x180's - well I have to replace the decoupling caps on two of them (blew them up by miswiring).

How much xformer would you recommend?

Regards,
Tom

[KeithC]

It depends on the impedence of your speakers. If this is 8ohms, 250VA is OK - incidentally, I presume you do appreciate that the 180s are actually more like 90s @ 8 ohm.

If your speakers are 4 ohm and you want to give 'em some welly, then around 400VA would be preferable.

How hot is your transformer running? If it is not getting v. warm it probably isn't running out of headroom. In which case I'd look at the reservoir capacitors on the ST rather than the transformer. I don't have experience with the ST, but they don't look to be over-endowed.

There has been a lot written on this forum concerning power supply requirements for the UcDs, well worth searching for.

[ptwining]

My speaks are 4ohm floor standers but the trannie isn't hot.

However - I notice that DIYAudio is now selling a 650VA xformer @ 2x30V secondaries specifically for the 180's.

Why is that if my 250VA is supposed to be enough?

Regards,
Tom

[classd4sure]

I'm not going to say the UCD's arent' thin sounding or lack SPL, they are and they can, but you're talking stock module, remember, the "industrial" version?

Before you can even begin to blame it on that though, give us a good look at your implementation.. quality of parts used and what exactly you did with them. It takes a somewhat optimal implementation to get the most out of them, and with a few tweaks the highs will be crystal, and the SPL numbing.

Aside from that, have you looked at the specs for your NAD at all?

2 x 120 Watts continuous power into 8ohms
210W, 340W, 450W Dynamic Power into 8, 4 and 2 ohms respectively

..are you comparing with the soft clipping feature enabled or disabled?

I'm really not a big fan of compressed dynamics and the kind of SPL that's there one second and gone the next.

Anyway, if you really want some slam, you can get some bigger transformers that will have tighter regulation and more instantaneous current capability, as a good start, use high quality parts nicely implemented, do something about those coupling electrolytics for cleaner highs, .... you'll be on your way to nirvana.

You could even be more extreme and fix your burnt modules, mod them both to the same spec as your others, and run them bridged. I gurantee you dynamic power and compression aside, it will blow your nad out of the water.

[ptwining]

The quality of the UCD is immaculate - NAD or no NAD.

I did read the specs and was comparing the NAD @ 2x120 to the UCD 2x180 figure - you're right in that the 180 @ 8ohms isn't a fair comparison. Fair enough.

I always ran the soft clipping on. Okay so I'm learning (grin).

I just posted KeithC about the new xformers that DIYAUdio is selling. They sold me the 250VA and have now upped their standard product to the 650VA. Is that something I should do?

I'll send a pic of my UCD implementation so you can see what's up. Gotta find my teeny-tiny camera. Too easily lost these iPod sized goodies. (smile).

Regards,
Tom